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Full text of "The manufacture and properties of iron and steel"

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process of making steel begins by making pig-iron^ from iron ore. \ This iron ore is natural iron rust. It is a combination of iron and oxygen, and if we take away the oxygen the iron is left alone. Charcoal or coke or carbon in any form will rob iron ore of its oxygen, and it will do this at a very moderate temperature, the action taking place if the ore and coke are mixed and heated red hot. But it is necessary to do more than this. The iron must be melted and the earthy parts of the ore and coke must be separated from the iron. The operation is conducted in. a furnace about one hundred feet high, filled with a mixture of coke, iron ore and limestone, and superheated air is blown in at the bottom. A portion of the coke is burned by the oxygen of the air and serves to maintain the furnace at a high temperature, while another portion is employed in robbing the iron ore of its oxygen.
The air that is blown into the furnace is first heated to a dull red heat by passing it through "stoves." These stoves are in turn heated by burning in them the gases escaping from the top of the furnace. In ancient days these gases were allowed to escape freely, but now the tops are closed tight and all the gas is taken down to the level of the ground, part being used under boilers to generate steam to run the blowing engines, and part in the stoves to preheat the blast.
As the air is red hot when it enters the tuyeres, and as it immediately meets glowing coke which has been heated by its downward passage through the furnace, it follows that a very high temperature must be caused at this point. This region, therefore, immediately about the tuyeres is called the "zone of fusion/' It is here that the real melting occurs, but a great deal of the work is done higher up in the furnace, for the gases from this hot zone of fusion ascend through the overlying 70 or 80 feet of stock and .heat it to a high temperature, and under these conditions there is a reaction